Laser diodes are used in optical transmission systems as light emitters. FIG. 1 illustrates a conventional laser diode behavior. Conventional laser diodes generate a characteristic optical power curve 110, in which three ranges can be distinguished. A pre-threshold portion A having a slight slope, in which there is no emission yet of coherent light. A “threshold area” B, which has a “knee” in the characteristic curve. Finally, a steeper portion of the characteristic curve includes a linear portion 111 having a constant slope, in which there is a linear correlation between the driving current and the optical power output.
Temperature changes affect diode behavior. For example, the second laser power curve 120 depicts the optical performance of the same laser diode at a higher temperature. The characteristic curve appears to shift to the right (as indicated by the arrow). Additionally, the slope of the linear portion commonly becomes shallower. Also, the threshold current values increase.
Thus, when the operating points (e.g., operating current levels I0, I1) are set for a diode at one particular temperature they are valid for the diode only as long as it remains at the same temperature. However, in ordinary course of operation diode temperatures can fluctuate significantly. As shown in FIG. 1 this leads to significant changes in diode operating parameters (e.g., threshold current, optical power output, diode slope efficiency, as well as many other significant operating parameters). This makes calibration and operating points set at one temperature invalid at other temperatures. What is needed is method and apparatus for trimming and compensating for the effects of changing temperature. Moreover, it would be desirable to have a method and apparatus capable of utilizing previously obtained laser characterization data to facilitate the set up and compensation schemes of the present invention. Additionally, it would be desirable to have an optical link having a laser apparatus capable of utilizing previously obtained laser characterization data to operate the laser using previously generated temperature and laser performance information to adjust the laser operating performance in accordance with changes in temperature to accommodate pre-defined operating conditions for the optical link.